Step block



FIG. 1 is a perspective view of a step block having my new design;

FIG. 2 is a side view thereof;

FIG. 3 is a top view thereof

FIG. 4 is a right side view thereof;

FIG. 5 is a bottom view thereof; and,

FIG. 6 is a back view thereof. 

The ornamental design for a step block, substantially as shown and described. 